Parathyroid scintigraphy in patients with primary hyperparathyroidism: 99mTc sestamibi SPECT and SPECT/CT

Endocrine radionuclide scintigraphy with fusion single photon emission computed tomography/computed tomography

AIM: To review the benefits of single photon emission computed tomography (SPECT)/computed tomography (CT) hybrid imaging for diagnosis of various endocrine disorders.

METHODS: We performed MEDLINE and PubMed searches using the terms: “SPECT/CT”; “functional anatomic mapping”; “transmission emission tomography”; “parathyroid adenoma”; “thyroid cancer”; “neuroendocrine tumor”; “adrenal”; “pheochromocytoma”; “paraganglioma”; in order to identify relevant articles published in English during the years 2003 to 2015. Reference lists from the articles were reviewed to identify additional pertinent articles. Retrieved manuscripts (case reports, reviews, meta-analyses and abstracts) concerning the application of SPECT/CT to endocrine imaging were analyzed to provide a descriptive synthesis of the utility of this technology.

RESULTS: The emergence of hybrid SPECT/CT camera technology now allows simultaneous acquisition of combined multi-modality imaging, with seamless fusion of three-dimensional volume datasets. The usefulness of combining functional information to depict the bio-distribution of radiotracers that map cellular processes of the endocrine system and tumors of endocrine origin, with anatomy derived from CT, has improved the diagnostic capability of scintigraphy for a range of disorders of endocrine gland function. The literature describes benefits of SPECT/CT for ^99mTc-sestamibi parathyroid scintigraphy and ^99mTc-pertechnetate thyroid scintigraphy, ¹²³I- or ¹³¹I-radioiodine for staging of differentiated thyroid carcinoma, ¹¹¹In- and ^99mTc- labeled somatostatin receptor analogues for detection of neuroendocrine tumors, ¹³¹I-norcholesterol (NP-59) scans for assessment of adrenal cortical hyperfunction, and ¹²³I- or ¹³¹I-metaiodobenzylguanidine imaging for evaluation of pheochromocytoma and paraganglioma.

CONCLUSION: SPECT/CT exploits the synergism between the functional information from radiopharmaceutical imaging and anatomy from CT, translating to improved diagnostic accuracy and meaningful impact on patient care.

Ectopic Parathyroid Adenoma in the Carotid Sheath

Primary hyperparathyroidism is predominantly caused by a single parathyroid adenoma. Knowledge of normal and ectopic locations of parathyroid glands is crucial to help guide surgeons who plan targeted unilateral parathyroidectomy to reduce surgical time and risk. We describe a female patient with clinical primary hyperparathyroidism who underwent a failed initial parathyroidectomy, with subsequent imaging localizing an ectopic parathyroid adenoma in the carotid sheath.

Is Brown Adipose Tissue Visualization Reliable on 99mTc-Methoxyisobutylisonitrile Diagnostic SPECT Scintigraphy?

The 99mTc-MIBI has been used with great value as a diagnostic technique in patients with primary hyperparathyroidism. False-positive scans may occur due to misinterpretation of the physiologic distribution of the 99mTc-MIBI. Reviewing consecutive SPECT scans, we evaluated this possibility and assessed how frequently brown adipose tissue (BAT) is seen on 99mTc-MIBI scintigraphy. Here, we retrospectively reviewed scans of consecutive patients who were evaluated for parathyroid adenomas from March 2015 to June 2015, using dual-phase (early and delayed) planar imaging and SPECT. We identified 60 patients (48 female and 12 male; mean age, 52.25 ± 15.20 years; range, 22-86 years).We detected the presence of 99mTc-MIBI uptake in BAT in 20 of 60 patients (33.33%) in the neck. Although the patients with T99mc-MIBI uptake in BAT were younger (mean age, 48.85 ± 15.27 years, range, 26-73 years) than the patients with no 99mTc-MIBI uptake (mean age, 53.95 ± 15.07 years, range, 22-86 years), this difference was not statistically significant (P = 0.224). The percentage of female patients with BAT detection was higher (17/48 patients; 37.5%) than that of the male population (3/12 patients; 25%), this difference was not also statistically significant (P = 0.85).In patient population referred to 99mTc MIBI scintigraphy of the parathyroid glands, uptake of 99mTc-MIBI in BAT should not be misinterpreted with 99mTc-MIBI-avid-tumors. Fused SPECT/CT images (not SPECT-only) are necessary to distinguish BAT from bone, muscle, thyroid, myocardium, parathyroids, and other structures in the neck and chest.

Parathyroid adenoma localization with 99mTc-sestamibi SPECT/CT: a meta-analysis

PURPOSE

The aim of the study was to determine the diagnostic utility of parathyroid scintigraphy with technetium-99m (99mTc)-sestamibi single-photon emission computed tomography/computed tomography (SPECT/CT) for localization of parathyroid adenoma.

MATERIALS AND METHODS

We performed a systematic search of medical databases PubMed and Medline/OVID for literature on 99mTc-sestamibi SPECT/CT parathyroid scintigraphy, using the search terms hyperparathyroidism, parathyroid adenoma/hyperplasia, SPECT/CT, and SPECT-CT. Citations for 981 articles and 128 abstracts of full articles were reviewed by two coauthors for relevance. Twenty-four peer-reviewed studies on SPECT/CT parathyroid scintigraphy qualified for inclusion. The Quality Assessment of Diagnostic Accuracy Studies-2 tool was used to assess study quality. Meta-analytical techniques were used to obtain pooled estimates of the parathyroid adenoma localization rate using a random-effects model.

RESULTS

A total of 24 studies published between January 2003 and March 2014 with 1276 patients (334 men, 762 women, and 180 of unspecified sex) met the inclusion criteria. Data on the test performance of dual-phase 99mTc-sestamibi SPECT/CT showed an estimated pooled sensitivity (per-patient analysis) of 0.86 [confidence interval (CI) 0.81-0.90]. Sensitivity of SPECT/CT was superior to that of SPECT (0.74; CI 0.66-0.82) and planar (0.70; CI 0.61-0.80) techniques. Heterogeneity was present in the reported literature (I2=80.3%). The rate of ectopic parathyroid adenomas ranged between 4 and 20% and SPECT/CT was superior to SPECT and planar imaging for localization of ectopic sites.

CONCLUSION

Utilization of SPECT/CT fusion imaging for 99mTc-sestamibi parathyroid scintigraphy improves the test performance compared with planar and SPECT imaging; it assists preoperative planning for a minimally invasive surgical approach for the neck and is of value in subgroups with ectopic glands or coexisting nodular thyroid disease.

Parathyroid Imaging with Simultaneous Acquisition of 99mTc-Sestamibi and 123I: The Relative Merits of Pinhole Collimation and SPECT/CT

The objective of this study was to determine the relative utility of 3 state-of-the-art parathyroid imaging protocols: single-time-point simultaneous acquisition of (99m)Tc-sestamibi and (123)I images with pinhole collimation in the anterior and bilateral anterior oblique projections, single-time-point simultaneous acquisition of (99m)Tc-sestamibi and (123)I images with SPECT/CT, and the combination of the first and second protocols.

METHODS

Fifty-nine patients with surgical proof of parathyroid adenomas were evaluated retrospectively. All 3 protocols included perfectly coregistered subtraction images created by subtracting the (123)I images from the (99m)Tc-sestamibi images, plus an anterior parallel-hole collimator image of the neck and upper chest. The pinhole protocol was performed first, followed by the SPECT/CT protocol. Three image sets were derived from each study in each patient according to the above protocols. Two experienced observers recorded the size, location, and degree of certainty of any identified lesion.

RESULTS

The 59 patients had 61 adenomas. For the 2 observers combined, the localization success rate was 88% for the pinhole protocol, 69% for the SPECT/CT protocol, and 81% for the combined protocol. The pinhole protocol detected more adenomas than the SPECT/CT protocol and missed fewer adenomas than either the SPECT/CT protocol or the combined pinhole and SPECT/CT protocol (P < 0.01). The 2 protocols that included SPECT/CT provided superior anatomic information relative to the location and size of the parathyroid adenomas.

CONCLUSION

The pinhole protocol localized significantly more adenomas than the SPECT/CT protocol. However, the protocols that included SPECT/CT provided more anatomic information than pinhole imaging alone.

Sporadic multiple parathyroid gland disease--a consensus report of the European Society of Endocrine Surgeons (ESES)

BACKGROUND

Sporadic multiglandular disease (MGD) has been reported in literature in 8-33 % of patients with primary hyperparathyroidism (pHPT). This paper aimed to review controversies in the pathogenesis and management of sporadic MGD.

METHODS

A literature search and review was made to evaluate the level of evidence concerning diagnosis and management of sporadic MGD according to criteria proposed by Sackett, with recommendation grading by Heinrich et al. and Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system. Results were discussed at the 6th Workshop of the European Society of Endocrine Surgeons entitled 'Hyperparathyroidism due to multiple gland disease: An evidence-based perspective'.

RESULTS

Literature reports no prospective randomised studies; thus, a relatively low level of evidence was achieved. Appropriate surgical therapy of sporadic MGD should consist of a bilateral approach in most patients. Unilateral neck exploration guided by preoperative imaging should be reserved for selected patients, performed by an experienced endocrine surgeon and monitored by intraoperative parathormone assay (levels of evidence III-V, grade C recommendation). There is conflicting or equally weighted levels IV-V evidence supporting that cure rates can be similar or worse for sporadic MGD than for single adenomas (no recommendation). Best outcomes can be expected if surgery is performed by an experienced parathyroid surgeon working in a high-volume centre (grade C recommendation). Levels IV-V evidence supports that recurrent/persistence pHPT occurs more frequently in patients with double adenomas hence in situations where a double adenoma has been identified, the surgeon should have a high index of suspicion during surgery and postoperatively for the possibility of a four-gland disease (grade C recommendation).

CONCLUSIONS

Identifying preoperatively patients at risk for MGD remains challenging, intraoperative decisions are important for achieving acceptable cure rates and long-term follow-up is mandatory in such patients.

Primary hyperparathyroidism in pregnancy leading to hypercalcaemic crisis and uraemic encephalopathy

Primary hyperparathyroidism is rare during pregnancy. Recognition may be challenging as symptoms overlap with those of other common disorders of pregnancy. Furthermore, physiological changes of pregnancy affecting calcium homoeostasis mean awareness of the condition and careful interpretation of results in the light of pregnancy are essential for diagnosis. Maternal complications of primary hyperparathyroidism include nephrolithiasis, pancreatitis, cardiac arrhythmias, hypertension and peptic ulcers. At its most severe, hypercalcaemic crisis may occur, presenting with acute neurological disturbance. Most commonly, the underlying aetiology is a solitary parathyroid adenoma whereby parathyroidectomy is the only cure. A 30-year-old Caucasian woman booked under Consultant care presented at 32 weeks gestation with vomiting and right-sided loin pain. Following presentation, she was diagnosed with renal calculi. She was delivered by caesarean section (CS) due to deterioration in renal function. Post-CS, she had a grand mal seizure. She was found to have hypercalcaemia with underlying hyperparathyroidism.

Optimization and evaluation of reconstruction-based compensation methods and reconstruction parameters for Tc-99m MIBI parathyroid SPECT

The value of Tc-99m MIBI parathyroid SPECT for localizing parathyroid hyperplasia in chronic renal failure patients remains inconclusive due to limited image quality. Advanced reconstruction methods to improve image quality have been developed but require optimization and evaluation. The goal of this study was to optimize and evaluate compensation methods and reconstruction parameters for Tc-99m MIBI parathyroid SPECT. A phantom population and projection data that modelled clinically realistic variations found in patients were simulated. The 3D OS-EM reconstruction with compensation for attenuation, detector response and scatter in various combinations were studied. For each compensation, the number of updates for OS-EM and the cutoff frequency of a 3D Butterworth filter were optimized and evaluated using anthropomorphic model observer. With optimal parameters, the method with compensation for attenuation and detector response, with or without the addition of scatter compensation, provided the highest lesion detectability for Tc-99m MIBI parathyroid SPECT.

Endocrine scintigraphy with hybrid SPECT/CT

Nuclear medicine imaging of endocrine disorders takes advantage of unique cellular properties of endocrine organs and tissues that can be depicted by targeted radiopharmaceuticals. Detailed functional maps of biodistributions of radiopharmaceutical uptake can be displayed in three-dimensional tomographic formats, using single photon emission computed tomography (CT) that can now be directly combined with simultaneously acquired cross-sectional anatomic maps derived from CT. The integration of function depicted by scintigraphy and anatomy with CT has synergistically improved the efficacy of nuclear medicine imaging across a broad spectrum of clinical applications, which include some of the oldest imaging studies of endocrine dysfunction.

Vignette hyperparathyroidism: glimpse into its history

The parathyroid gland was first described by Sir Richard Owen. Ivor Sandstrom coined the term glandulae parathyroidiae. Vassale and Generali Francesco observed that tetany occurs following parathyroidectomy. Harald Salvesen firmly established the relationship of the parathyroid gland to calcium metabolism. A patient with skeletal disease and a tumor near the parathyroid gland was described by Max Askanazy in 1904. Schlagenhaufer suggested in 1915 that in an attempt to cure bone disease, solitary parathyroid enlargement, if present, should be excised. The term hyperparathyroidism (HPT) was coined by Henry Dixon and colleagues. The parathyroid surgeries on Albert J. and Charles Martell were the first experience with successful parathyroidectomy. From a grossly symptomatic disease of bones, stones, abdominal groans, and psychic moans, HPT has evolved into asymptomatic HPT. Improvements in knowledge about the pathology of parathyroid diseases, including the genetic basis of HPT, and advances in the surgical techniques have brought about changes in the management of HPT over the decades.

Comparison of 99mTc-sestamibi and 11C-methionine PET/CT in the localization of parathyroid adenomas in primary hyperparathyroidism

AIM

To evaluate the usefulness of (11)C-methionine PET/CT (MET) in the localization of the parathyroid adenomas and to compare the results with those obtained with the conventional technique in double-phase (99m)Tc-sestamibi scintigraphy (MIBI). We evaluated the optimal timing to acquire MET images.

MATERIAL AND METHODS

A prospective study that included 14 patients (mean age: 65.5 ± 9.7 years) with primary hyperparathyroidism (PH) who underwent surgery was performed. Mean serum iPTH was 215.8 ± 108 pg/mL and serum calcium 10.8 ± 0.9 mg/dL. MIBI (planar and SPECT) was obtained 10 min and 2-3h after injection of 740 MBq (20 mCi) of (99m)Tc-sestamibi. MET was obtained 10 min and 40 min after injection of 740 MBq (20 mCi) of (11)C-methionine. MIBI and MET images were visually evaluated and compared. A score for 10 min and 40 min MET images from 0 (no abnormal uptake) to 3 (intense uptake) was assigned.

RESULTS

MIBI and MET were positive and concordant in 11/14 patients and in 10 of them the parathyroid adenoma was correctly localized. In 3/14 MIBI was positive and MET negative (MIBI correctly localized the parathyroid adenoma in 2 of them). According to the timing of MET imaging acquisition, the 10 min and 40 min acquisition showed the same score in 10 patients, it was higher at 10 min acquisition in 3 and in 1 the parathyroid adenoma was only detected at 40 min acquisition.

CONCLUSION

MIBI remains the technique of choice for the localization of parathyroid adenomas in patients with PH. MET may play a complementary role in selected patients. Delayed acquisition should be included in the MET protocol when the early acquisition is negative.

Preoperative Localization of Parathyroid Adenomas Using 4-Dimensional Computed Tomography: A Pictorial Essay

Accurate preoperative localization is the key to successful parathyroid surgery in the era of minimally invasive parathyroid surgery. This article presents and discusses the embryologic basis of parathyroid gland and ectopic location and different imaging modalities helpful in diagnosing and localizing parathyroid adenomas and/or hyperplasia. We also aim to review the current surgical concepts in treatment of parathyroid adenomas and/or hyperplasia, the utility of 4-dimensional computed tomography for accurate preoperative localization of hyperfunctioning parathyroid glands, imaging classification of adenomas and/or hyperplasia, and, finally, present some of the limitations of 4-dimensional computed tomography.

Spectral Doppler analysis of parathyroid adenoma: correlation between resistive index and serum parathyroid hormone concentration

OBJECTIVE

The purpose of this study was to evaluate the correlation between spectral wave analyses by measuring the resistive index and serum intact parathyroid hormone (iPTH) concentration in primary hyperparathyroidism.

SUBJECTS AND METHODS

From March 2008 to April 2012, 46 consecutively registered patients underwent color and spectral Doppler ultrasonography for determination of vascularity and vascular resistance of parathyroid adenoma. The color Doppler sonographic findings were compared with methoxyisobutylisonitrile (MIBI) scintigraphic findings, serum iPTH concentration, and the volume of the gland.

RESULTS

The mean resistive index in parathyroid adenoma was 0.69 ± 0.12. The study showed a strong negative relation between resistive index and serum iPTH concentration. There was a significant negative relation between the volume of the gland and the resistive index.

CONCLUSION

There is a relation between degree of perfusion in parathyroid adenoma and serum iPTH concentration. Resistive index may be an objective alternative parameter for determining the vascularity of adenoma for monitoring of response to alcohol ablation therapy and medical management.

Detection and Characterization of Parathyroid Adenoma/Hyperplasia for Preoperative Localization: Comparison Between (11)C-Methionine PET/CT and (99m)Tc-Sestamibi Scintigraphy

PURPOSE

(11)C-Methionine PET/CT (Met-PET/CT) is a useful imaging method for detection of parathyroid adenoma; however, the reported detection rate has been variable. The current study was intended to investigate detection sensitivity and preoperative localization of parathyroid adenoma (PA) or parathyroid hyperplasia (PH) on Met-PET/CT compared with (99m)Tc-sestamibi (MIBI) scintigraphy in patients with primary hyperparathyroidism (HPT) or suspected PA.

METHODS

Met-PET/CT and MIBI scintigraphy images were reviewed by two nuclear medicine physicians unaware of pathologic results. Detection sensitivities and preoperative localization of detected parathyroid tissues into five predefined segments were evaluated by visual assessment and semi-quantitative analysis with ratio of standardized uptake values (SUVR) between parathyroid tissue and normal lung as reference. Linear regression analysis with SUVR and serum parathyroid hormone (sPTH) was performed for characterization of PA or PH. Predicted PTH (pPTH) was calculated and compared with sPTH in PH and PA. Each pPTH was obtained for a calculated SUVR by using linear regression model from the result of previous linear regression analysis between SUVR and sPTH.

RESULTS

In 16 patients, detection sensitivities of Met-PET/CT and MIBI scintigraphy were 91.7 % (11/12) and 41.7 % (5/12) for PA and PH including both biopsy-confirmed and clinically-suspected cases, and 100 % (8/8) and 50 % (4/8) for pathologically confirmed PA and PH cases only, respectively. Met-PET/CT showed higher performance than MIBI scintigraphy in localization of parathyroid tissues; correct localization rate was 87.5 % (7/8) on Met-PET/CT and 50 % (4/8) on MIBI scintigraphy. In semi-quantitative analysis, SUVR was linearly associated with sPTH by linear regression analysis (sPTH = 39.53 × SUVR - 89.84, p = 0.0383). There was a borderline significant difference in pPTH between PH and PA (35.1 vs 204.7 ± 164.0, p = 0.052), while there was no significant difference in sPTH between PH and PA (289 vs 230.4 ± 160.4, p = 0.305).

CONCLUSIONS

Met-PET/CT has a potential to be a useful diagnostic modality for preoperative detection and localization of parathyroid tissues with higher sensitivity than MIBI scintigraphy, and for characterization of PA or PH.

A spectrum of SPECT/CT image fusion applications in daily clinical practice

Direct multimodality image correlation optimizes interpretation and diagnostic confidence, thereby enriching the radiologist's role in guiding clinical management. The primary advantages of SPECT/CT image fusion are more accurate identification and localization of disease and improved specificity. As illustrated here, software-based SPECT/CT image fusion enhances diagnosis for a variety of clinical presentations using the armamentarium of common radiopharmaceuticals, but without the costs of hybrid systems.

Use of (99m)Tc 2-methoxyisobutyl isonitrile in minimally invasive radioguided surgery in patients with primary hyperparathyroidism: A narrative review of the current literature

The use of technetium-99m 2-methoxyisobutyl isonitrile (^99mTc MIBI) for assistance in minimally invasive radioguided surgery (MIRS) is growing in popularity as a safe, effective, and proficient technique used for parathyroidectomy in primary hyperparathyroidism (PHPT) treatment. Previously, the preferred treatment for PHPT was bilateral neck exploration (BNE), a very invasive, costly, and lengthy procedure. However, as a large majority (80–85% of cases of PHPT) are attributed to a single parathyroid adenoma (PA), a simpler more direct technique such as MIRS is a far better option. The following article is an exploration of the current literature concerning varied protocols utilizing ^99mTc MIBI for assistance in MIRS for patients undergoing treatment of PHPT. This technique boasts many advantageous outcomes for patients suffering from PHPT. These include a reduction in cost, operating time, and patient recovery; less evidence of post-surgical hypocalcaemia, less pain, and complications; superior cosmetic results; same-day discharge; and the possibility of local anaesthesia which is particularly beneficial in elderly patients. Better outcomes for patients with deep or ectopic PAs, reduced intra-operative complications, and improved cosmetic outcomes for patients who have previously undergone thyroid and/or parathyroid surgery are also advantageous. Of the literature reviewed it was also found that no patients suffered any major surgical complications such as laryngeal nerve palsy or permanent hypoparathyroidism using ^99mTc MIBI for assistance in MIRS.

Planar scintigraphy with 123I/99mTc-sestamibi, 99mTc-sestamibi SPECT/CT, 11C-methionine PET/CT, or selective venous sampling before reoperation of primary hyperparathyroidism?

All patients with primary hyperparathyroidism should undergo localization studies before reoperation, but it is not known which method is most accurate. The purpose of this prospective study was to compare the performance of planar scintigraphy with (123)I/(99m)Tc-sestamibi, (99m)Tc-sestamibi SPECT (SPECT/CT), (11)C-methionine PET/CT, and selective venous sampling (SVS) in persistent primary hyperparathyroidism.

METHODS

Twenty-one patients referred for reoperation of persistent hyperparathyroidism were included and investigated with (123)I/(99m)Tc-sestamibi, SPECT/CT (n = 19), (11)C-methionine PET/CT, and SVS (n = 18) before reoperation. All patients had been operated on 1-2 times previously because of hyperparathyroidism. The results of the localization studies were compared with operative findings, histology, and biochemical cure.

RESULTS

Eighteen (86%) of 21 patients were biochemically cured. Nineteen parathyroid glands (9 adenomas, 1 atypical adenoma, and 9 hyperplastic glands) were removed from 17 patients, and 1 patient who was biochemically cured had an unclear histology result. The accuracy for localizing a pathologic parathyroid gland to the correct side of the neck was 59% (95% confidence interval [CI], 36%-79%) for (123)I/(99m)Tc-sestamibi, 19% (95% CI, 5%-42%) for SPECT/CT, 65% (95% CI, 43%-84%) for (11)C-methionine PET/CT, and 40% (95% CI, 19%-65%) for SVS (P < 0.01 for (123)I/(99m)Tc-sestamibi vs. SPECT/CT). The corresponding accuracy for the correct quadrant or more specific site was 48% (95% CI, 27%-69%) for (123)I/(99m)Tc-sestamibi, 14% (95% CI, 3%-36%) for SPECT/CT, 61% (95% CI, 39%-80%) for (11)C-methionine PET/CT, and 25% (95% CI, 9%-49%) for SVS (P < 0.02 for (123)I/(99m)Tc-sestamibi vs. SPECT/CT). In the 3 patients not cured, preoperative (123)I/(99m)Tc-sestamibi and SPECT/CT remained negative, SVS was false predictive in all, and (11)C-methionine PET/CT in 1. (11)C-methionine PET/CT accurately revealed the pathologic gland in 4 of 8 (50%) patients with a negative (123)I/(99m)Tc-sestamibi scan result, all of whom were biochemically cured after reoperation.

CONCLUSION

Planar scintigraphy with (123)I/(99m)Tc-sestamibi performs well in complicated primary hyperparathyroidism and is recommended as first-line imaging before reoperation. (11)C-methionine PET/CT provides valuable additional information if (123)I/(99m)Tc-sestamibi scan results remain negative. (99m)Tc-sestamibi SPECT/CT and SVS provide no additional information, compared with the combined results of (123)I/(99m)Tc-sestamibi and (11)C-methionine PET/CT imaging.

Preoperative ⁹⁹mTc-sestamibi scintigraphy in patients with primary hyperparathyroidism and concomitant nodular goiter: comparison of SPECT-CT, SPECT, and planar imaging

BACKGROUND

Investigations using a hybrid single photon emission computed tomography/computed tomography (SPECT-CT) scanning technique have been carried out in limited studies and have shown mixed results. However, the assessment of this technique for the detection of parathyroid adenoma in patients with a nodular goiter was performed in only one study with a small sample size. The aim of this prospective study was to assess the role of 99mTc-sestamibi parathyroid SPECT-CT scans for localization of parathyroid adenomas with a concomitant nodular goiter using 99mTc-methoxyisobutyl isonitrile (MIBI) scintigraphy and to compare it with SPECT and planar imaging.

METHODS

This study was conducted on 48 patients with primary hyperparathyroidism and nodular goiter, who were candidates for parathyroid surgery and had been referred for parathyroid scintigraphy. The patients underwent an early set of planar 99mTc-MIBI scanning procedures first, followed by SPECT and CT scannings, and finally a delayed set of planar 99mTc-MIBI scannings. Sensitivity, specificity, negative and positive predictive values, and accuracy were determined on a per-parathyroid-gland basis for each scanning method, as defined by histology and follow-up.

RESULTS

The surgery was successful in 48 out of 50 patients with primary hyperparathyroidism concomitant with thyroid nodularity, and data were completed for 80 sites in 48 patients. The accuracy of SPECT-CT in correctly identifying a parathyroid adenoma was 85.00, versus 75.00% for SPECT (P=0.01, significant). The sensitivity and specificity for SPECT-CT were 77.55 and 96.77%, respectively, versus 67.34 and 87.09%, respectively, for SPECT (P=0.12 and 0.12, not significant). There were nine sites that showed better localization on SPECT-CT scans relative to SPECT images, of which five sites were located in the ectopic regions.

CONCLUSION

The results of our study indicate that SPECT-CT is more accurate than sestamibi planar imaging and SPECT for the preoperative identification of parathyroid lesions in patients with primary hyperparathyroidism concomitant with thyroid nodularity. Also, we would recommend the use of SPECT-CT for a workup of all patients with ectopic glands who are scheduled for minimally invasive parathyroid surgery.

Improved localization of sestamibi imaging at high-volume centers

OBJECTIVES/HYPOTHESIS

Sestamibi imaging can provide critical information regarding the location of suspected parathyroid adenomas. However, this modality can be challenging to perform and interpret reliably. The impact of experience on the localizing efficacy of sestamibi scanning was assessed.

STUDY DESIGN

Prospective analysis of a consecutive series of patients undergoing parathyroidectomy was undertaken after institutional review board approval was obtained.

METHODS

Patients undergoing parathyroid surgery from October 2003 through June 2011 were considered. Inclusion criteria represented primary surgery for primary hyperparathyroidism, in which a single adenoma was excised and cure obtained. Sestamibi scan results, performed at our institution and at outside imaging centers, were compared to intraoperative findings.

RESULTS

There were 389 parathyroidectomies performed; 188 patients met inclusion criteria. Fifty-four patients had sestamibi scans performed at outside institutions; 36 (67%) were localizing and 18 (33%) were nonlocalizing. Among localizing studies, half identified the correct quadrant and half recognized the correct side. At our institution, 147 patients underwent sestamibi imaging; 121 (82%) localized and 26 (18%) did not. Among localizing studies, the correct quadrant was reported in 64% and the correct side in 36%. Of the 147 scans performed at our institution, 13 represented repeat scans of patients with nonlocalizing outside scans. All 13 of these localized; six identified the correct quadrant and seven the side of the adenoma.

CONCLUSIONS

A high volume of experience may improve the yield of sestamibi imaging. Repeating this study at a high-volume center when it was nonlocalizing elsewhere may provide useful additional information.

Anatomical and functional imaging in endocrine hypertension

In endocrine hypertension, hormonal excess results in clinically significant hypertension. The functional imaging (such as radionuclide imaging) complements anatomy-based imaging (such as ultrasound, computed tomography, and magnetic resonance imaging) to facilitate diagnostic localization of a lesion causing endocrine hypertension. The aim of this review article is to familiarize general radiologists, endocrinologists, and clinicians with various anatomical and functional imaging techniques used in patients with endocrine hypertension.

Can SPECT change the surgical strategy in patients with primary hyperparathyroidism?

Primary hyperparathyroidism (PHPT) is the most common cause of hypercalcemia in outpatients. It is more common in females, after menopause, and the prevalence is 1 to 4:1000 in the general population. Patients with PHPT have abnormal regulation of PTH secretion, resulting in elevated serum calcium and inappropriately high or normal PTH in relation to the calcium value. Sporadic PTH-secreting adenoma alone accounts for 90% of cases of PHPT, while multiglandular hyperplasia is more common in familial hyperparathyroidism syndromes (5%) and parathyroid carcinomas represent less than 1% of cases. Only after making sure there is functional autonomy of one or more parathyroid glands, localization imaging tests should be performed to guide a possible surgical procedure. It is important to highlight that these tests have limitations and can yield false-positive and false-negative results. There are cases in which the parathyroid gland is difficult to be located, requiring a combination of imaging methods for pre-operative localization, such as (99m)Tc-pertechnetate, SPECT, SPECT/CT, and US. We describe the case of a 50-year-old female patient diagnosed with PHPT, who underwent a surgical procedure without success, with maintenance of hypercalcemia and hyperparathyroidism. In this case, the hyperfunctioning parathyroid was located in the retrotracheal region only after scintigraphy combined with SPECT/CT were used.

Imaging techniques in parathyroid surgery for primary hyperparathyroidism

As more patients present with the incidental diagnosis of primary hyperparathyroidism due to biochemical screening, treatment guidelines have been developed for the treatment of hyperparathyroidism. Management of primary hyperparathyroidism has evolved in recent years, with considerable interest in minimally invasive approaches. Successful localization of the diseased gland(s) by nuclear imaging and anatomical studies, along with rapid intraoperative parathyroid hormone assay, has allowed for focused and minimally invasive surgical approaches. Patients in whom the localization studies have identified single-gland adenoma or unilateral disease are candidates for such focused approaches instead of the traditional approach of bilateral exploration. These imaging techniques have also been critical in the successful management of patients with persistent or recurrent disease.

Optimizing the minimally invasive approach to mediastinal parathyroid adenomas

BACKGROUND

Patients with refractory hyperparathyroidism after neck exploration may have a mediastinal parathyroid gland that has not been identified reliably with a single radiologic study. We report 17 patients who underwent minimally invasive resection for mediastinal parathyroid adenomas after confirmatory multipoint radiologic imaging.

METHODS

Fifteen patients underwent thoracoscopic procedures and 2 patients underwent mediastinoscopic procedures for resection of suspected mediastinal parathyroid adenoma. Preoperative localizing studies included sestamibi scan, computed tomography scan of the neck and chest, and selective venous sampling of parathyroid hormone levels. Once a mediastinal location was determined, thoracoscopic or mediastinoscopic resection was performed. Successful removal of parathyroid tissue was confirmed with a 50% or greater reduction in intraoperative parathyroid hormone levels.

RESULTS

Parathyroid adenoma was resected in 88% of patients after the operation. The cure rate was 100% in patients with two or more concordant studies locating parathyroid tissue in the mediastinum and 60% in those with one positive study. The thoracostomy tube was removed on median postoperative day 1 (range, 0 to 2 days). Median hospital stay was 3 days (range, 2 to 7 days). The most common complication was temporary hypocalcemia, which occurred in 18% of patients.

CONCLUSIONS

Minimally invasive parathyroidectomy is an effective treatment of hyperparathyroidism caused by mediastinal parathyroid tissue. Targeted exploration depends on the guidance of preoperative localization studies and measurement of intraoperative parathyroid hormone levels to verify successful resection. Selective venous sampling and high-resolution computed tomography scanning can be helpful in patients with negative sestamibi scans.

Outpatient management of primary hyperparathyroidism

Primary hyperparathyroidism is the most common cause of hypercalcemia in an outpatient setting. Most patients are asymptomatic with mild hypercalcemia and only require periodic follow-up. Symptomatic patients and those with end-organ damage should undergo surgery according to the National Institutes of Health guidelines. No medical therapy has been approved for treatment of this disorder. Treatment with bisphosphonate, calcimimetic drugs, or alcohol ablation techniques has been used in select patients.

Imaging characteristics of hyperfunctioning parathyroid adenomas using multiphase multidectector computed tomography: a quantitative and qualitative approach

OBJECTIVE

The objective of the study was to characterize the enhancement pattern of hyperfunctioning parathyroid adenomas on multiphase multidetector computed tomography (CT) or 4-dimensional CT.

METHODS

We retrospectively studied the enhancement patterns of 48 pathologically confirmed parathyroid adenomas with 4-dimensional CT, compliant with institutional review and the Health Insurance Portability and Accountability Act. Region-of-interest analysis was done at baseline and at arterial (25 seconds), venous (55 seconds), and delayed (85 seconds) enhancement phases over the adenoma and adjacent normal thyroid tissue. Qualitative and quantitative analysis was done. Discriminant functions were calculated using a multivariate logistic regression model, and receiver operating characteristic curves were measured.

RESULTS

Adenomas are lower than thyroid in density, demonstrate avid early contrast enhancement, and show rapid wash-out of contrast. Adenomas and thyroid had baseline Hounsfield unit attenuations of 35 ± 11 and 94 ± 21 and enhancement percentage change from baseline to arterial of 493% ± 328% and 132% ± 148%, respectively (P < 0.0001 both). Quantitative analysis showed that these 2 measures of baseline density and the percentage change from baseline to arterial were the most powerful discriminatory features, with contrast wash-out from arterial peak to venous phase being a less powerful discriminator. Several discriminant functions were derived, the best of which was: X = 13.74 - (0.207 × baseline Hounsfield unit) - (0.006 × percent density change from baseline to arterial). X > 0.2 classifies tissue as parathyroid with high certainty (area under the receiver operating characteristic curve = 0.98; specificity, 0.938; sensitivity, 0.999).

CONCLUSIONS

Parathyroid adenomas have a characteristic enhancement pattern that can be distinguished from thyroid tissue: the key diagnostic discriminators are baseline density, percentage change in density from baseline to arterial enhancement, and percentage decrease in density from arterial to venous phases.

Minimally Invasive Parathyroid Surgery, The Norman 20% Rule: Is It Valid?

The 20 per cent rule proposed by Norman established a guideline using radioactivity in the minimally invasive radioguided parathyroidectomy (MIRP) technique to localize and confirm removal of an abnormal parathyroid gland in patients with primary hyperparathyroidism. If radioactivity in the resected gland was at least 20 per cent of excision site/background radioactivity, the 20 per cent rule was satisfied. Patients meeting these criteria underwent unilateral MIRP without intraoperative parathyroid hormone assay or intraoperative frozen section. The study aim was to independently evaluate the 20 per cent rule in MIRP patients with primary hyperparathyroidism. Using the University of Louisville Parathyroid Database from January 1, 1999 to December 31, 2007, 216 MIRP patients with complete radioguided and postoperative management data were identified. The average percentage of ex vivo parathyroid gland radioactivity compared with excision site/background radioactivity was 107 per cent with a range from 14 to 388 per cent. For 99 per cent (196/198) radioactivity recorded from the excised gland was at least 20 per cent of radioactivity recorded from the excision site. Normocalcemia was documented in 98.5 per cent (195/198) at 12 month follow-up. Our data supports the 20 per cent rule in that in 99 per cent of MIRP patients the resected gland radioactivity was at least 20 per cent of excision site radioactivity allowing localization and confirmation of an overactive gland without intraoperative parathyroid hormone monitoring or tissue analysis.

Intraoperative adjuncts for parathyroid surgery

In recent years, parathyroid surgery has evolved from traditional bilateral neck exploration to minimal invasive parathyroidectomy. This trend became possible due to preoperative localization imaging that guides the surgeon in the search for a parathyroid adenoma. Intraoperative adjuncts are complementary to preoperative localization and assist in localizing parathyroid glands, confirming parathyroid tissue and establishing a cure. Institutions and surgeons utilize different intraoperative adjuncts in different protocols with varying results. The purpose of this article is to review the available intraoperative adjuncts to parathyroid surgery and critically evaluate their utility, accuracy and their added value to the surgeon.

Validity of dual tracer 99mTc-tetrofosmin and 99mTc-pertechnetate subtraction parathyroid scintigraphy in patients with primary and secondary hyperparathyroidism

BACKGROUND/AIM

Primary hyperparathyroidism (pHPT) is an endocrine disease with the third highest incidence of all endocrine disorders after diabetes mellitus and hyperthyroidism. pHPT is typically caused by a solitary parathyroid adenoma, less frequently by multiple parathyroid gland disease (MGD) and rarely by parathyroid carcinoma. Secondary hyperparatyroidism (sHPT) is a common complication in patients with chronic renal failure. The aim of this study was to estimate sensitivity of dual tracer 99mTc-tetrofosmin and 99mTc-pertechnetate subtraction scintigraphy in detection of abnormal parathyroid glands in patients with pHPT and sHPT confirmed by histopathology.

METHODS

In 46 patients, (77 abnormal parathyroid glands), 30 with pHPT and 16 with sHPT parathyroid scintigraphy was done preoperatively. All the patients had histopathological confirmation of diagnosis. Abnormal parathyroid glands weighted from 0.1 to 7 g. After iv injection dynamic scintigraphy during 25 minutes (one frame-one minute) using 555 MBq of 99mTc-tetrofosmin, and three hours latter using 111 MBq of 99mTc/pertechnetate was performed. 99mTc-tetrofosmin dynamic study was followed by static scintigraphy of the neck and chest 30 minutes, 1, 2 and 3 hours after iv injection.

RESULTS

An abnormal scintigraphic finding was found in 44 of 46 patients with sensitivity of 96%. In pHPT sensitivity was 93% (28 of 30 patients, and 28 of 30 glands). In sHPT scintigraphy was abnormal in all the patients (sensitivity 100%). In the patients with sHPT scintigraphy detected 30 of 47 abnormal parathyroid glands (sensitivity 64%). An overall sensitivity of scintigraphy per gland, for pHPT and sHPT in detecting 58 of 77 abnormal parathyroid glands was 75%.

CONCLUSION

An abnormal scintigraphic result per patient was found in 44 patients (sensitivity 96%) and 58 of 77 abnormal parathyroid glands were detected (sensitivity 750/0). A high sensitivity of dual tracer subtraction 99mTc-tetrofosmin/99mTc-pertechnetate parathyroid scintigraphy in detecting abnormal parathyroid glands in primary and secondary hyperparathyroidism was achieved.

Surgical management of primary hyperparathyroidism: state of the art

This article reviews the current state of the art regarding therapy for primary hyperparathyroidism. Clinical evaluation and indications for parathyroidectomy are described, followed by a review of surgical techniques currently being practiced and possible outcomes involved. Focused parathyroidectomy has become a successful alternative to conventional bilateral cervical exploration.